Gil Kalai’s blog

Believing that the Earth is Round When it Matters

A world map. Canada seems much bigger than Israel. Note, however, that in the map countries near the equator looks smaller than they are. Update: The round-earth hypothesis is clearer to the people of New Zealand; see the comments section.

One difficult aspect of the academic life is the requirement to fly to conferences and other academic activities all over the world. Strangely, speaking about this hardship to non- academic friends does not always elicit the sympathy we deserve.

Last month, I had to be on duty in two places outside Jerusalem. The first was a conference in Beijing and the second was a conference and a visit in the the Los Angeles area. My solution was to make a round trip to Beijing and another round trip to LA. (I am simplifying matters since there was some interference due to additional travels, visa matters, etc..)

I discovered the following flaws I make in planning my trips:

1) I am (somewhat) biased toward round trips.

More seriously…

2) I dont take into account that the earth is round.

The book solution to this travel was to go from Jerusalem to Beijing and then from Beijing to Los Angeles and from LA to Jerusalem. I completely ignored this possibility. When I realized it, it made me wonder what this reveals about my true beliefs regarding the round earth hypothesis.

Believing that this coffee cup is a realistic model of the world suffices to prefer the Beijing-LA solution over two round-trips solution!

Remark: As a matter of fact in order to think of the possibility to fly from Beijing to LA one does not have to be as advanced as to believe in the “round earth hypothesis”. It is enough to believe that the world is either round or a cylinder so that the right and left boundaries of the world map are glued together.

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16 thoughts on “Believing that the Earth is Round When it Matters”

Hmmm. Where I am from (NZ) a round-the-world ticket is standard. And it is also clear that the world is round: if you go from Sydney to Copenhagen via Japan, there is a flight from Tokyo to Copenhagen over the north pole via Anchorage. It is difficult to understand why other people make this all so complicated, but I have actually met many northerners who don’t even know that our seasons are out of phase with yours. This is truly a Dark Age.

Thats a good idea. Maybe such an application already exist somewhere on the web? We can prepare a map like the one in the post by prescribing two places one (Chicago, say) to center of the map and one (Jerusalem, say) for the up direction.

What about Archimedes hat-box theorem? Is it not actually saying that the surface measure on a shpere equals the measure on a cylinder, and a map is it not a flattened cylinder? Then countries near poles should look proportionally to the scale as big as they are (only distorted in shape) if presumably the map gives the correct projection.

Niz, one could produce maps that preserve the area (using a suitable projection). But, the projections most frequently used for maps do not. (As the area-preserving maps, do not preserve other things one cares about, and it is impossible to preserve ‘everything.’)

Today, I went to the beach front with my children. I found a sea shell and
gave it to my 4 year old daughter and said “You can hear the ocean if you put this to your ear.” She placed the shell to her ear
and screamed. There was a hermit crab inside and it
pinched her ear. She never wants to go back! LoL I know this is entirely off
topic but I had to tell someone!